Month: August 2016

MySQL vs. PostgreSQL, gh-ost perspective

MySQL

Last week we released gh-ost, GitHub’s online schema migration tool for MySQL. As with other open source releases in the MySQL ecosystem, this release was echoed by several “Why not PostgreSQL?” comments. Having been active in open source since many years now, I’m familiar with these responses, and I find this is a good time to share my thoughts. Why? XKCD knows the answer:

XKCD: Duty Calls

I picked one post I wish to address (latest commit: 3dfbd2cd3f5468f035ec86442d2c670a510118d8). The author invested some time writing it. It nicely summarizes claims I’ve heard over the years, as well as some prejudice. Through responding to this post I will be generalizing thoughts and impressions to address the common reactions. Dear @brandur, let’s grab a beer some day; I fundamentally disagree with your post and with its claims.

EDIT: linked post has been updated following this writing; I’d like to thank the author for his consideration. Also see his followup post. The version I’ve responded to in this post is this commit. Continue reading Ā» “MySQL vs. PostgreSQL, gh-ost perspective”

Introducing gh-ost: triggerless online schema migrations

MySQL

I’m thoroughly happy to introduce gh-ost: triggerless, controllable, auditable, testable, trusted online schema change tool released today by GitHub.

gh-ost now powers our production schema migrations. We hit someĀ serious limitations using pt-online-schema-change on our large volume, high trafficĀ tables, to the effect of driving our database to a near grinding halt or even to the extent of causing outages. With gh-ost, we are now able to migrate our busiestĀ tables at any time, peak hours and heavy workloads included, without causing impact to our service.

gh-ost supports testing in production. It goes a long way to build trust, both in integrity and in control.Ā Are your databases just too busy and you cannot run existing online-schema-change tools? Have you suffered outages due to migrations? Are you tired of babysitting migrations that run up to 3:00am? Tired of being the only one tailing logs? Please, take a look at gh-ost. I believe it changes online migration paradigm.

For a more thorough overview, please read the announcement on the GitHub Engineering Blog, and proceed to the documentation.

gh-ost is open sourced under the MIT license.